The cat left the dock under tow about 9.30am, headed north towards Tiritiri Matangi Island and the Noises 30km north of Auckland.

Testing stopped when minor damage – a broken rib in the front element of the wing – brought the day to a premature end.

Grant Dalton: 'We had a good two hours of upwind testing in 12 knots of breeze and flat water before the break. The boat is under extreme loads…. we could go out there every day and break something different.

'It’s just part of the process of getting the boat up to speed.'

'Today we had to decide if we could continue testing, make a temporary repair on shore and go back out or make a permanent repair.

'The engineers made the prudent call to fix the rib permanently so we stayed ashore.'

With the wing out of the boat it is a simple repair. Late this afternoon the team was assessing if the weather forecast would allow a return to the Gulf tomorrow but opted for early next week when the weather forecast promises to deliver the breeze they want.

The early stages of the sailing programme is designed to test boat and wing structures under various loads as well as giving the sailing crew valuable boat time.

Dalton: 'The programme’s purpose is to uncover any stress points while they are only niggles - before they can develop into an issue. That’s why structural engineers and wing designers sail with us as we test in progressively heavier winds.

'The designers have the world’s best computer-modeling software tools at their disposal but they are never satisfied until they see a yacht sailing on the real-world test bed of the Hauraki Gulf.'

'It won’t be long before the engineers stay on shore and the sailing team is let loose.'

Emirates Team New Zealand sailing the AC72 on the Hauraki Gulf on the second day of sailing. A bang brings an end to sailing as a part in the wing gives way.Richard Meacham goes aloft to check the damage and take some photos for the designers. 3/8/2012